Dynamic configuration of a flexible orthogonal frequency division multiplexing PHY transport data frame

ABSTRACT

A base station may generate and transmit a transport stream including a sequence of frames. A frame may include a plurality of partitions, where each partition includes a corresponding set of OFDM symbols. For each partition, the OFDM symbols in that partition may have a corresponding cyclic prefix size and a corresponding FFT size, allowing different partitions to be targeted for different collections of user devices, e.g., user devices having different expected values of maximum delay spread and/or different ranges of mobility. The base station may also dynamically re-configure the sample rate of each frame, allowing further resolution in control of subcarrier spacing. By allowing the cyclic prefixes of different OFDM symbols to have different lengths, it is feasible to construct a frame that confirms to a set payload duration and has arbitrary values of cyclic prefix size per partition and FFT size per partition. The partitions may be multiplexed in time and/or frequency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/222,817,filed Jul. 28, 2016, which is a continuation of application Ser. No.14/821,107, filed Aug. 7, 2015, and claims priority under 35 U.S.C.119(e) from U.S. Provisional Patent Application No. 62/034,583 filed onAug. 7, 2014, all of which are incorporated by reference herein in theirentireties.

FIELD OF THE DISCLOSURE

The present disclosure relates to the field of wireless communication,and more particularly, to mechanisms for dynamically constructingOrthogonal Frequency Division Multiplexing (“OFDM”) physical transportframes, to enable flexibility in configuration of transmissions inbroadcast networks.

DESCRIPTION OF THE RELATED ART

In today's world, many electronic devices rely upon wirelessconnectivity for the reception of data from other connected devices. Ina typical wireless deployment, there may be one or more wireless accesspoints that transmit data, and one or more devices that receive datafrom the wireless access point(s).

In such a scenario, different devices may have different propagationchannel characteristics, and these may affect their wireless datareception from the same wireless access point. For example, a devicethat is near the wireless access point and/or that has a fixed location(or is slowly moving) may have better propagation channel conditionsthan would a device that is moving at a high velocity and/or that isfurther away from the wireless access point. The first device may fallinto a group of devices that can receive data encoded and transmittedwith one set of parameters (such as a high Forward Error Correction(FEC) code rate, a high modulation level, and/or a smaller subcarrierspacing in an Orthogonal Frequency Division Multiplexing (hereinafterreferred to as “OFDM”) system, while the second device may fall into agroup of devices that need data to be encoded and transmitted with asecond set of parameters (such as a low FEC code rate, a low modulationlevel, and/or a wider subcarrier spacing in an OFDM system).

There are many scenarios where a large number of devices may all wish toreceive identical data from a common source. One such example isbroadcast television, where a large number of television sets in varioushomes all receive a common broadcast signal conveying a program ofinterest. In such scenarios, it is significantly more efficient tobroadcast or multicast the data to such devices rather than individuallysignaling the same data to each device. However, programs with differentquality levels (e.g. high definition video, standard definition video,etc) may need to be transmitted to different groups of devices withdifferent propagation channel characteristics. In other scenarios, itmay be desirable to transmit device-specific data to a particulardevice, and the parameters used to encode and transmit that data maydepend upon the device's location and/or propagation channel conditions.

As described above, different sets of transmitted data may need to betransmitted with different encoding and transmission parameters, eithersimultaneously or in a time-multiplexed fashion (or both). The amount ofdata to be transmitted in a particular data set and/or the encoding andtransmission parameters for that data set may vary with time.

At the same time, the demand for high-speed wireless data continues toincrease, and it is desirable to make the most efficient use possible ofthe available wireless resources (such as a certain portion of thewireless spectrum) on a potentially time-varying basis.

SUMMARY

Modern and future high-speed wireless networks must be designed forefficient handling of a variety of deployment scenarios. Presentlydisclosed are mechanisms that enable broad flexibility in wireless datadelivery, to support services in a full range of deployment scenarios,which might include, but are not limited, to the following: receivermobility (e.g. fixed, nomadic, mobile); cell size (e.g. macro, micro,pico); single or multiple frequency networks (SFN or MFN); multiplexingof different services; and bandwidth sharing.

A. In one set of embodiments, a method for constructing and transmittinga frame having a specified temporal length may be implemented asfollows. The method may enable flexibility in configuring transmissionsfrom a base station.

The method may include performing operations using digital circuitry ofthe base station, wherein said operations include: (a) for each of oneor more partitions of the frame, determining a corresponding OFDM symbollength for OFDM symbols belonging to the partition, wherein the OFDMsymbol length is based on a corresponding FFT size and a correspondingcyclic prefix size, wherein the corresponding cyclic prefix sizesatisfies a size constraint based on a corresponding minimum guardinterval duration; (b) computing a sum of OFDM symbol lengths in a unionof the OFDM symbols over the partitions; (c) computing a number ofexcess samples based on the sum and a length of a payload region of theframe; and (d) constructing the frame.

The action of constructing the frame may include, for each OFDM symbolin the union, assigning the OFDM symbol to exactly one of at least onesubset of the union using at least one of the number of excess samplesand an index of the OFDM symbol, and adding a number to the cyclicprefix size of each OFDM symbol in each of the at least one subset ofthe union, prior to embedding the OFDM symbols in the frame, wherein aunique number is used for each of the at least one subset of the union.

The method may also include transmitting the frame over a wirelesschannel using a transmitter of the base station.

In some embodiments, the action of constructing the frame also includes,for one of the at least one subset of the union, setting the uniquenumber for that subset to zero.

In some embodiments, one of the at least one subset of the unionrepresents an initial contiguous subset of the OFDM symbols in theunion.

In some embodiments, the at least one subset of the union and the uniquenumber for each of the at least one subset of the union are determinedaccording to an algorithm known to remote devices that receive saidtransmissions.

B. In one set of embodiments, a method for constructing and transmittinga frame by a base station may be implemented as follows.

The method may include performing operations using digital circuitry ofthe base station, where the operations include constructing a payloadregion of the frame. The payload region includes a plurality ofpartitions, wherein each of the partitions includes a correspondingplurality of OFDM symbols, wherein each partition has a correspondingFFT size and a corresponding cyclic prefix size for OFDM symbols in thatpartition.

The method may also involve transmitting the frame over a wirelesschannel using a transmitter of the base station.

In some embodiments, the operations also include embedding signalinginformation in a non-payload region of the frame, wherein the signalinginformation indicates the FFT size and the cyclic prefix size for eachof the partitions.

In some embodiments, each of the partitions includes a corresponding setof overhead resource elements (such as reference symbols). In theseembodiments, the operations may also include scheduling symbol data fromone or more service data streams to each of the partitions after havingreserved the overhead resource elements within the frame.

In some embodiments, a first of the partitions is targeted fortransmission to mobile devices, and, a second of the partitions istargeted for transmission to fixed devices. In these embodiments, theFFT size corresponding to the first partition may be smaller than theFFT size corresponding to the second partition.

In some embodiments, a first of the partitions is targeted fortransmission to first user devices that are expected to have large delayspreads, and a second of the partitions is targeted for transmission tosecond user devices that are expected to have smaller delay spreads. Inthese embodiments, the cyclic prefix size for the first partition may belarger than the cyclic prefix size for the second partition.

In some embodiments, the frame may be partitioned according to one ormore others factors in addition to (or, as an alternative to) theabove-described partitioning according to the expected user mobility andrequired cell coverage as determined by FFT size and cyclic prefix size.For example, factors may include a data rate, wherein differentpartitions have different data rates. In particular, differentpartitions may have a high data rate or a low data rate (along the linesof Internet of Things), with a lower duty cycle for low power reception.In one example, factors may include tight vs. loose clustering wheretime diversity is sacrificed in the interest of allowing a low powerdevice to wake up, consume the data it needs, and then go back to sleep.In one example, factors may include frequency partitioning that allowsthe band edges to be coded more robustly using a lower modulation orderto permit band shaping or other interference mitigation techniques.

C. In one set of embodiments, a method for constructing and transmittinga frame by a base station may be implemented as follows.

The method may include performing operations using digital circuitry ofthe base station, where the operations include: (a) constructing aplurality of partitions, wherein each of the partitions includes acorresponding set of OFDM symbols, wherein the OFDM symbols in eachpartition conform to a corresponding FFT size and satisfy acorresponding minimum guard interval; and (b) constructing a frame bytime interleaving the OFDM symbols of the partitions to form OFDM symbolclusters, wherein the OFDM symbol clusters are defined by: a specifiedvalue of OFDM symbol cluster size for each partition; and a specifiedvalue of OFDM symbol cluster period for each partition.

The method may also include transmitting the frame over a wirelesschannel using a transmitter of the base station.

In some embodiments, a first of the partitions is targeted fortransmission to mobile devices, and a second of the partitions istargeted for transmission to fixed devices. In these embodiments, theFFT size corresponding to the first partition may be smaller than theFFT size corresponding to the second partition.

In some embodiments, the above-described operations may also includeembedding signaling information in the frame, wherein the signalinginformation indicates the specified value of OFDM symbol cluster sizefor each partition and the specified value of OFDM symbol cluster periodfor each partition.

In some embodiments, a user device may be configured to: (1) receive theframe; (2) for a particular partition to which the user device has beenassigned, determine the corresponding specified values of OFDM symbolcluster size and OFDM symbol cluster period based on the signalinginformation in the frame; and (3) recover the OFDM symbols belonging toOFDM symbol clusters of the particular partition, using thecorresponding specified values.

D. In one set of embodiments, a method for constructing and transmittinga transport stream by a base station may be implemented as follows. Thetransport stream includes a frame.

The method may involve performing operations using digital circuitry ofthe base station, where the operations include: (a) constructing apayload region of the frame, wherein samples in the payload regioncorrespond to a specified sample rate, wherein the specified sample rateis selected from a universe of possible sample rates supported bytransmission circuitry of the base station, wherein the samples in thepayload regions are divided into one or more partitions, wherein each ofthe partitions includes a corresponding set of OFDM symbols; andembedding signaling information in the transport stream, wherein thesignaling information includes information indicating the specifiedsample rate.

The method may also include transmitting the transport stream over awireless channel using a transmitter of the base station.

In some embodiments, the specified sample rate has been specified by anoperator of a broadcast network that includes said base station.

In some embodiments, the above-described signaling information isembedded in a non-payload region of the frame. In an alternativeembodiment, the signaling information may be embedded in a previousframe of the transport stream.

In some embodiments, each partition has a corresponding value of FFTsize for OFDM symbols included in that partition.

In some embodiments, for each partition, the FFT size of that partitionand the user-specified sampling rate have been selected to define asubcarrier spacing for that partition that satisfies a specified minimumsubcarrier spacing (or Doppler tolerance) for that partition.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiments isconsidered in conjunction with the following drawings.

FIG. 1A illustrates one embodiment of a broadcast network including aplurality of base stations.

FIG. 1B illustrates one embodiment of an Orthogonal Frequency DivisionMultiplexing (“OFDM”) symbol with both a cyclic prefix and a usefulportion.

FIG. 2 illustrates an overview of an example frame structure.

FIG. 3A illustrates an example of Physical Partition Data CHannel(PPDCH) time multiplexing with distinct time separation of the PPDCH.

FIG. 3B illustrates an example Physical Partition Data CHannel (PPDCH)time multiplexing with distinct time separation of the PPDCH.

FIG. 4A illustrates an example of PPDCH time multiplexing with timeinterleaving of the PPDCH.

FIG. 4B illustrates an example of PPDCH time multiplexing with timeinterleaving of the PPDCH.

FIG. 5 illustrates the relationship between different physical channelsfor carrying payload data, according to one embodiment.

FIG. 6 illustrates PFDCH sampling rate varied on a per frame basis,according to one embodiment.

FIG. 7 illustrates an example of distributing excess samples to cyclicprefixes of OFDM symbols within the payload region of a frame, accordingto one embodiment.

FIG. 8 illustrates useful subcarriers within an OFDM symbol, accordingto one embodiment.

FIG. 9 illustrates an example of PPDCH frequency multiplexing, accordingto one embodiment.

FIG. 10 illustrates the layout of logical resources within a PPDCH,according to one embodiment.

FIG. 11 illustrates logical stripes and logical subbands within a PPDCH,according to one embodiment.

FIG. 12 illustrates a mapping of virtual stripes belonging to a virtualsubband to logical stripes belonging to a logical subband, according toone embodiment.

FIG. 13 illustrates an example rotation and mapping of virtual stripesto logical stripes, according to one embodiment.

FIG. 14 illustrates an example rotation and mapping of logical stripesto virtual stripes, according to one embodiment.

FIG. 15 illustrates an example of mapping a Physical Service DataCHannel (PSDCH) to virtual resources of a PPDCH, according to oneembodiment.

FIG. 16 illustrates an example of concatenated Physical Frame DataCHannel (PFDCH), PPDCH, and PSDCH descriptors for communication to areceiver, according to one embodiment.

FIG. 17 illustrates one embodiment of a method for constructing andtransmitting a frame by a base station, where the frame includes aplurality of partitions, each having a corresponding FFT size and acorresponding cyclic prefix size.

FIG. 18 illustrates one embodiment of a method for constructing andtransmitting a frame by a base station, where excess samples aredistributed to the cyclic prefixes of OFDM symbols in the frame.

FIG. 19 illustrates one embodiment of a method for constructing andtransmitting a frame by a base station, where the frame includes aplurality of partitions, each having a corresponding FFT size and acorresponding cyclic prefix size, wherein the partitions are timeinterleaved.

FIG. 20 illustrates one embodiment of a method for constructing andtransmitting a frame by a base station, wherein the sample rateassociated with payload regions of the frame is configurable.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE EMBODIMENTS List of Acronyms Used in thePresent Patent

-   ATS: Auxiliary Termination Symbols-   BG: Broadcast Gateway-   BS: Base Station-   CP: Cyclic Prefix-   CRC: Cyclic Redundancy Check-   DC: Direct Current-   FEC: Forward Error Correction-   FFT: Fast Fourier Transform-   IFFT: Inverse Fast Fourier Transform-   LDPC: Low Density Parity Check-   MAC: Medium Access Control-   MFN: Multi-Frequency Network-   MHz: Mega Hertz-   OFDM: Orthogonal Frequency Division Multiplexing-   PDU: Protocol Data Unit-   PHY PHYsical layer-   PFDCH: Physical Frame Data CHannel-   PPDCH: Physical Partition Data CHannel-   PSDCH: Physical Service Data CHannel-   QAM: Quadrature Amplitude Modulation-   RS: Reference Symbols-   SFN: Single Frequency Network    Broadcast Network Architecture

In one set of embodiments, a broadcast network 100 may be configured asshown in FIG. 1A. The broadcast network 100 may include a plurality ofbase stations 101 a, 101 b . . . 101 n, illustratively suggested by basestations BS₁, BS₂, . . . , BS_(N)(hereinafter referred to as basestations 101). A broadcast gateway (“BG”) 102 may couple to the basestations 101 through any of a variety of communication media. Forexample, in one embodiment, the broadcast gateway 102 may couple to thebase stations 101 via the Internet, or more generally, via a computernetwork. Each base station 101 wirelessly transmits information to oneor more user devices 103. (Each user device UD is denoted by a solidblock circle.) Some of the user devices 103 may be fixed devices such astelevisions and desktop computers. Other ones of the user devices 103may be nomadic devices such as tablet computers or laptop computers.Other ones of the user devices 103 may be mobile devices such as mobilephones, automobile-based devices, aircraft-based devices, etc.

An operator (“Op) 104 of the broadcast network 100 may access thebroadcast gateway 102 (e.g., via the Internet), and provide networkconfiguration or operating instructions to the gateway 102. For example,the operator 104 may provide information such as one or more of thefollowing items: an expected distribution of user device mobility forone or more of the base stations; the cell size of one or more of thebase stations; a selection of whether the broadcast network or a subsetof the network is to be operated as a single frequency network (SFN) ora multi-frequency network (MFN); a specification of how differentservices (e.g., television content streams) are to be assigned todifferent types of user devices; and identification of portions ofbandwidth the broadcast network will not be using over correspondingperiods of time.

The broadcast gateway may determine transmission control information forone or more base stations of the broadcast network based on the networkconfiguration or operating instructions. For a given base station, thebroadcast gateway may determine: transmission sample rate; number ofpartitions; sizes of the partitions; FFT size and cyclic prefix size foreach partition. The broadcast gateway may send the transmission controlinformation to the base stations so the base stations may construct andtransmit frames according to the transmission control information. Inother embodiments, the gateway may itself generate frames to betransmitted by each gateway and send the frames to the base stations. Inyet other embodiments, the gateway may generate low level instructions(e.g., physical layer instructions) for the construction of frames tothe base stations, and send those instructions to the base stations,which may simply generate frames based on the instructions.

OFDM Symbols and FFT/IFFT Sizes

An Orthogonal Frequency Division Multiplexing (OFDM) system uses anInverse Fast Fourier Transform (“IFFT”) operation at the transmitter toconvert frequency domain data to the time domain for transmission, and aFast Fourier Transform (“FFT”) operation at the receiver to convertreceived time domain values back to the frequency domain in order torecover the originally transmitted data. In the following text, the termFFT is generally used, but the parameters described correspond to thefrequency and time dimensions for both the FFT and IFFT operations.

For illustration purposes, an example base sampling rate of F_(S)=12.288MHz is generally used here. This is not meant to be limiting, and othersampling rates may also be used. The corresponding base time unitcorresponding to one sample is T_(S)=1/F_(S) seconds.

A range of different FFT/IFFT sizes and cyclic prefix lengths may besupported in order to address a wide variety of propagation conditionsand different end user scenarios. A separate entity such as a schedulermay select appropriate FFT/FFT size(s) and cyclic prefix length(s) foreach frame using the following guidelines.

First, the minimum subcarrier spacing needed to support the intendeduser mobility is determined. Higher mobile velocities result in largerDoppler shifts, which necessitate wider subcarrier spacing in frequency,Δf. The subcarrier spacing can be calculated as follows. This impliesthat larger FFT sizes would be used for fixed scenarios, and smaller FFTsizes would be used for mobile scenarios.

$\begin{matrix}{{\Delta\; f} = \frac{F_{S}}{{FFT}{\mspace{11mu}\;}{size}}} & {{equ}.\mspace{14mu}(1)}\end{matrix}$

Each OFDM symbol with a total time length of T_(sym) consists of twoparts, a cyclic prefix with a time length of T_(CP), and a usefulportion with a time length of T_(U), as shown in the example OFDM symbol102 illustrated in FIG. 1B. The useful portion 104 of the OFDM symbol102 refers to the amount of data corresponding to that which is requiredfor the IFFT/FFT operations. The cyclic prefix 106 is just a copy of thelast N_(CP) samples 108 of the useful portion 104 of the OFDM symbol andthus essentially represents overhead which is included in the OFDMsymbol 102.

The useful portion 104 of an OFDM symbol 102 has a number of timesamples equal to the size of the FFT (N_(FFT)), and a time length equalto:

$\begin{matrix}{T_{U} = {{{FFT}{\mspace{11mu}\;}{size} \times T_{S}} = \frac{1}{\Delta\; f}}} & {{equ}.\mspace{14mu}(2)}\end{matrix}$

The cyclic prefix 106 contains a specified number of samples (N_(CP))with a corresponding time length of T_(CP). The cyclic prefix 106consists of sample values copied from the end of the useful portion ofthe same OFDM symbol 102 and provides protection against inter-symbolinterference between successive OFDM symbols 102.

The number of subcarriers actually used within an FFT/IFFT depends onboth the subcarrier spacing (which is a function of the FFT size and thesampling frequency) and the bandwidth of the system, since the bandwidthoccupied by the used subcarriers must be less than the system bandwidth(in order to allow for a guard band between adjacent channels). Notealso that the direct current (DC) carrier is never used.

Table 1 shows a list of possible FFT sizes that can be used. FFT sizesthat are an integer power of 2 may be preferred in a wirelessimplementation for simplification reasons. The time length (T_(U))corresponding to the usable portion of each OFDM symbol 102, thesubcarrier spacing (Δf), and the maximum Doppler velocity that can behandled at an example carrier frequency of 700 MHz are also shown. Here,the maximum Doppler velocity is defined as the receiver velocity whichresults in a Doppler frequency shift equal to 10% of the subcarrierspacing. (It should be understood that the 10% used here is notessential to the presently disclosed inventions. Indeed, the percentagemay take any value in a range of values.) The values in this table arebased on the assumed example sampling frequency of 12.288 MHz.

TABLE 1 Example FFT sizes, useful portion time lengths, subcarrierspacings, and maximum Doppler velocities for an example sampling rate of12.288 MHz Maximum Doppler FFT Size T_(U) Δf velocity at 700 MHz(N_(FFT)) (μs) (Hz) (km/h) 1024 83 12000 1851 2048 167 6000 926 4096 3333000 463 8192 667 1500 231 16384 1333 750 116 32768 2667 375 58 655365333 188 29

Table 2 shows the same information for a different example sampling rateof 18.432 MHz. As can be seen, for a given FFT size, a sampling rate of18.432 MHz results in a shorter OFDM symbol length (T_(U)), a widersubcarrier spacing (Δf), and a higher maximum Doppler velocity which canbe handled, as compared to a sampling rate of 12.288 MHz.

TABLE 2 Example FFT sizes, useful portion time lengths, subcarrierspacings, and maximum Doppler velocities for an example sampling rate of18.432 MHz Maximum Doppler FFT Size T_(U) Δf velocity at 700 MHz(N_(FFT)) (μs) (Hz) (km/h) 1024 56 18000 2777 2048 111 9000 1389 4096222 4500 694 8192 444 2250 347 16384 889 1125 174 32768 1778 563 8765536 3556 281 43Cyclic Prefix Lengths and Cyclic Prefix Length Selection

Next, the cyclic prefix (“CP”) length may be selected to meet theintended range requirement. The cyclic prefix is used to addressinter-symbol interference between successive OFDM symbols. Suchinter-symbol interference arises from copies of the transmitted signalwith slightly different time delays arriving at the receiver, with suchcopies resulting from identical signal transmissions from multiple basestations in a Single Frequency Network (“SFN”) and/or reflections of atransmitted signal in a multi-path propagation environment.Consequently, in an SFN with significant distances between neighboringbase stations (or, potentially, in a propagation environment withsignificant multi-path scatter), a larger CP length would be selected.Conversely, in an SFN where neighboring base stations are closertogether, a shorter CP length may be used.

The CP length may be viewed as a percent relative to the overall OFDMsymbol length (giving the percent overhead consumed by the CP). However,for range planning, it is more useful to view the CP length as measuredin samples (as defined by the 12.288 MHz example sampling frequency).

Radio signals will propagate approximately 24.4 meters in the time ofone sample for the example sampling frequency of 12.288 MHz.

Table 3 gives the cyclic prefix lengths (in number of samples) andcorresponding ranges (in km) for various example cyclic prefix lengthsspecified relative to (as a percentage of) the useful portion of eachOFDM symbol. Again, the values in the table are based on the examplesampling frequency of 12.288 MHz.

TABLE 3 Example cyclic prefix lengths and corresponding ranges CyclicPrefix Length 1.56% 2.34% 3.13% 4.69% 6.25% 9.38% 12.5% # Range Range #Range # Range # Range # Range # N_(FFT) Samples (km) # Samples (km)Samples (km) Samples (km) Samples (km) Samples (km) Samples Range (km)1024 16 0.4 24 0.6 32 0.8 48 1.2 64 1.8 96 2.3 128 3.1 2048 32 0.8 481.2 64 1.6 96 2.3 128 3.1 192 4.7 256 6.3 4098 64 1.6 96 2.3 128 3.1 1924.7 256 6.3 384 9.4 612 12.5 8192 128 3.1 182 4.7 258 6.3 384 9.4 51212.5 768 18.8 1024 25.0 16384 256 6.3 384 9.4 512 12.5 768 18.8 102425.0 1536 37.5 2048 50.0 32768 512 12.5 768 18.8 1024 25.0 1536 37.62048 50.0 3072 75.0 4096 100.0 65536 1024 25.0 1536 37.5 2048 50.0 307275.0 4096 100.0 6144 150.0 8192 200.0

The above cyclic prefix lengths should be considered to be illustrativeexamples only. In particular, cyclic prefix lengths should notnecessarily be considered to be restricted to be a power of two (or evena multiple of a power of two). Cyclic prefix lengths may have anypositive integer value.

Payload Data Terminology

In a wireless system, data may generally be transmitted in a series offrames, which represent a certain period of time. FIG. 2 shows anoverview of the general frame structure. A frame 202 can be divided intoa payload region 204 which carries actual payload data and zero or morenon-payload regions 206 and 208 which may carry control or othersignaling information. In the example of FIG. 2, separate non-payloadregions 206 and 208 are shown by the shaded areas at the beginning andend of the frame 202. The relative lengths in time (horizontal axis) andnumbers of symbols for each region are not shown to scale in thisexample diagram.

The payload section 204 of the frame may be referred to as the PhysicalFrame Data CHannel (“PFDCH”) and carries the actual payload data (asopposed to control or other signaling data) being transmitted by a basestation. For illustrative purposes, it can be assumed that each frame202 has a time length of 1 second and that the payload region (PFDCH)204 has a time length of 990 ms, but these example lengths are not meantto be limiting.

An OFDM wireless frame 202, particularly the payload portion 204, isdivided into OFDM symbols in the time dimension and sub-carriers in thefrequency dimension. The most basic (time-frequency) unit of datacarrying capability in OFDM is a resource element, which is defined asone sub-carrier in the frequency dimension by one OFDM symbol in thetime dimension. Each resource element can carry one QAM modulationsymbol (or QAM constellation).

The number of sub-carriers available for a fixed system bandwidthdepends on the subcarrier spacing, which is in turn dependent upon theselected FFT size and sampling frequency. The time length of an OFDMsymbol is also dependent upon the selected FFT size and also upon theselected cyclic prefix length and sampling frequency. The number of OFDMsymbols available within a fixed period of time (such as the length of aframe) is dependent upon the time lengths of the individual OFDM symbolscontained within that period of time.

The PFDCH 204 may be divided into one or multiple partitions or PhysicalPartition Data Channel (hereinafter referred to as “PPDCHs”). A PPDCH isa rectangular logical area measuring some number of sub-carriers in thefrequency dimension and some number of OFDM symbols within the timedimension. A PPDCH need not span the full frequency bandwidth of thesystem, or the full time length of the PFDCH 204. This allows multiplePPDCHs to be multiplexed in time and/or frequency within the same PFDCH204.

Different PPDCHs may have, but are not constrained to have, differentFFT sizes and/or different cyclic prefix lengths. The primary intentbehind dividing a PFDCH 204 into multiple PPDCHs is to support theprovision of services to different categories of terminals. For example,fixed terminals may be served program data via a PPDCH with a large FFTsize and closer subcarrier spacing, while mobile terminals may be servedprogram data via a different PPDCH with a smaller FFT size and widersubcarrier spacing.

FIGS. 3A and 3B shows two examples of partitioned PFDCHs 302 and 310,respectively. These example configurations use the previously statedexample frame length of 1 second and PFDCH length of 990 ms, which leavea 10 ms non-payload region at the beginning of each example frame. Inthe example illustrated in FIG. 3A, two PPDCHs 304 and 306 use differentFFT sizes and may be intended to serve nomadic and fixed users,respectively. In the example illustrated in FIG. 3B, three PPDCHs 312,314 and 316 use different FFT sizes and may be intended to serve mobile,nomadic, and fixed users, respectively. The same cyclic prefix length asmeasured in samples may be used for all of the PPDCHs if the desiredtransmit ranges for different categories of users are desired to be thesame. However, there is no constraint requiring the same cyclic prefixlength to be used across multiple PPDCHs, so the configured cyclicprefix length may vary from one PPDCH to another, and the use ofdifferent cyclic prefix lengths for different PPDCHs may in fact bedesirable for certain wireless provisioning scenarios.

It should be appreciate that although FIG. 3 shows a strict timeseparation between the different PPDCHs when time multiplexing is used,OFDM symbols or OFDM symbol clusters from different PPDCHs can betime-interleaved with each other to maximize time diversity for a givenframe configuration, as shown in FIGS. 4A and 4B. In FIG. 4A, a PFDCH402 is partitioned in a time-interleaved fashion with OFDM symbolclusters 404 belonging to a first PPDCH, and OFDM symbol clusters 406belonging to a second PPDCH. In FIG. 4B, a PFDCH 412 is partitioned in atime-interleaved fashion with OFDM symbol clusters 414 belonging to afirst PPDCH, OFDM symbol clusters 416 belonging to a second PPDCH, andOFDM symbol clusters 418 belonging to a third PPDCH.

There are advantages to each of the above approaches. With a strict timeseparation such as in FIGS. 3A and 3B, a receiving terminal only needsto activate its radio for a portion of each frame, which can lead toreduced power consumption. With time interleaving such as shown in FIGS.4A and 4B, greater time diversity can be achieved.

Although the PPDCHs in FIGS. 3A and 3B and FIGS. 4A and 4B are the samesize, there is no requirement for PPDCHs within the same frame to be ofthe same length. Indeed, since different modulation levels and coderates are likely to be used within different PPDCHs, the data carryingcapacities of different PPDCHs may also be very different.

Each PPDCH within a frame may contain zero or more Physical Service DataCHannels (hereinafter referred to as “PSDCH”). It should be appreciatedthat part or all of the physical resources within a PPDCH may be leftunused. The contents of a PSDCH are encoded and transmitted using aspecified set of physical resources within the corresponding PPDCH. EachPSDCH contains exactly one transport block for data carrying purposes. Atransport block may correspond to a Medium Access Control (“MAC”)Protocol Data Unit (“PDU”) and represents a set of data bytes from upperlayers to be transmitted.

The relationship between the various payload-related physical channelsis illustrated in FIG. 5. Each frame contains one PFDCH 502. The PFDCH502 contains one or more PPDCHs 504. Each PPDCH 504 contains zero ormore PSDCHs 506.

Variable Sampling Rate on a Per Frame Basis

Although an example sampling rate of 12.288 MHz has generally been usedhere for illustrative purposes, it has already previously been statedthat this is not meant to be limiting and other sampling rates may alsobe used.

In particular, the sampling rate used for the data payload portion of aframe (i.e. the PFDCH) may be allowed to vary on a per frame basis. Thatis, a non-payload region such as 206 shown in FIG. 2 would use a fixedsampling rate (such as 12.288 MHz) which is known at a receiver. Thisnon-payload region 206 may signal control information which informs thereceiver as to the sampling rate which is used for the PFDCH 204 of thesame frame 202. FIG. 6 shows an example of this control signaling. Inframe 550, a sampling rate of 12.288 MHz to be used for the PFDCH 554 issignaled via control information in non-payload region 552. In frame560, a sampling rate of 18.432 MHz to be used for the PFDCH 564 issignaled via control information in non-payload region 562. In frame570, a sampling rate of 15.36 MHz to be used for the PFDCH 574 issignaled via control information in non-payload region 572.

FIG. 6 is intended to be illustrative only, and the use of and signalingof other sampling rates are not precluded. In another embodiment, PFDCHsampling rates may follow a fixed pattern For example, the PFDCHs ofodd-numbered frames may use a lower sampling rate such as 12.288 MHz,while the PFDCHs of even-numbered frames may use a higher sampling ratesuch as 18.432 MHz. This can be either predetermined or signaled toreceiving devices. In yet another embodiment, the sampling rates to beused for received PFDCHs may be signaled separately to receivers ratherthan being included in control signaling contained within the sameframe.

Distribution of Excess Samples to Cyclic Prefixes

In a physical sense, the PFDCH consists of a number of consecutivesamples in the time domain. This number of samples is equal to the totalnumber of samples in one frame minus the lengths in samples of anynon-payload regions of the same frame. For example, there may be 12.288million samples for the example sampling frequency of 12.288 MHz andexample frame length of 1 second.

After the lengths of the OFDM symbols contained within the PFDCH havebeen determined, it is quite likely that the total number of samplesconsumed by these OFDM symbols may be less than the total number ofsamples assigned to the PFDCH. Depending upon the PFDCH partitioning asdescribed earlier, OFDM symbols belonging to different PPDCHs may havedifferent lengths due to differing FFT sizes and/or cyclic prefixlengths, and it is likely to be an impossible task to ensure that thesum of their lengths exactly equals the number of samples expected to beconsumed by the PFDCH. However, it is disadvantageous to placeconstraints on FFT size selection, cyclic prefix length selection,and/or PFDCH partitioning into multiple PPDCHs, since this wouldseverely reduce the flexibility that is desired for configuring aparticular wireless frame. A method for using up any excess samples isrequired.

The exact number of excess samples (N_(excess)) to be dealt with for aparticular PFDCH can be calculated as:

$\begin{matrix}{N_{excess} = {N_{payload} - {\sum\limits_{i = 0}^{N_{{sym} - 1}}N_{i}}}} & {{equ}.\mspace{14mu}(3)}\end{matrix}$where: N_(payload) is the number of samples assigned to the PFDCH;N_(sym) is the total number of OFDM symbols in the PFDCH (indexing ofOFDM symbols begins at 0); and N_(i) is the number of samples in the ithOFDM symbol (equal to the corresponding FFT size plus the specifiedcyclic prefix length in samples). Note that not all of the OFDM symbolsin a PFDCH may be the same size if multiple PPDCHs (with different FFTsizes and/or cyclic prefix lengths) are present.

The above equation can be simplified to:

$\begin{matrix}{N_{excess} = {N_{payload} - {\sum\limits_{p = 0}^{N_{{PPDCH} - 1}}{N_{p,{sym}} \times \left( {N_{p,{FFT}} + N_{p,{CP}}} \right)}}}} & {{equ}.\mspace{14mu}(4)}\end{matrix}$where: N_(payload) is the number of samples assigned to the PFDCH;N_(PPDCH) is the total number of PPDCHs in the PFDCH (indexing of PPDCHsbegins at 0); N_(p,sym) is the total number of OFDM symbols configuredfor the p^(th) PPDCH; N_(p,FFT) is the FFT size configured for thep^(th) PPDCH; and N_(p,CP) is the cyclic prefix length in samplesconfigured for the p^(th) PPDCH.

FIG. 7 illustrates one example embodiment for distributing excesssamples 602. In particular, the cyclic prefix lengths 604 for the firstN_(excess) mod N_(sym) OFDM symbols within the PFDCH are each extendedby ┌N_(excess)/N_(sym)┐ samples 606. In addition, the cyclic prefixlengths 604 for the last N_(sym)−(N_(excess) mod N_(sym)) OFDM symbolswithin the PFDCH are each extended by └N_(excess)/N_(sym)┘ samples 606.

It should be appreciated that other embodiments for distributing theexcess samples among the OFDM symbols within the PFDCH are alsopossible. For example, a value N, where N<N_(sym), may be eithersignaled or predetermined. In order to distribute the excess samples,the cyclic prefix lengths for the first N OFDM symbols within the PFDCHare each extended by └N_(excess)/N┘ samples. In addition, the cyclicprefix length for PFDCH OFDM symbol N+1 is extended byN_(excess)−N×└N_(excess)/N┘ samples.

It will be appreciated by those skilled in the art that furtheradditional embodiments for distributing the excess PFDCH samples may beeasily derived.

Payload Structure and Mapping

This section gives a detailed specification as to how the PFDCH of awireless frame is structured, how payload partitions (PPDCHs) arespecified, how PSDCHs are mapped to specific physical resources, etc. Assuch, the contents of this section build on the concepts that wereintroduced earlier.

The key element behind the design is the concept of mapping virtualresources to logical resources and then logical resources to physicalresources.

Payload Partition Mapping

In a physical sense, the PFDCH consists of a number of consecutivesamples in the time domain. This number of samples is equal to the totalnumber of samples in one frame of any non-payload regions in the frame.For example, there may be 12.288 million samples for the examplesampling frequency of 12.288 MHz and example frame length of 1 second.

In a logical sense, the PFDCH is composed of a number of OFDM symbols inthe time domain and a number of subcarriers in the frequency domain. Thesum of the lengths in samples of all OFDM symbols within the PFDCH priorto excess sample distribution to cyclic prefixes must be less than orequal to the number of samples available for the PFDCH as calculatedabove.

OFDM symbols belonging to the same PPDCH will essentially have the samelengths, subject to excess sample distribution to cyclic prefixes, butOFDM symbols belonging to different PPDCHs may have different lengths.Consequently, not all OFDM symbols within the PFDCH will necessarilyhave the same length.

Similarly, the number of subcarriers in the frequency domain is afunction of the system bandwidth and the subcarrier spacing. Thesubcarrier spacing is dependent upon the selected FFT size and thesampling frequency, and may thus vary from one PPDCH to another, ifdistinct FFT sizes are configured for the two PPDCHs.

Different PPDCHs may be multiplexed in time and/or frequency.

Each PPDCH may be referenced via an index (e.g. PPDCH #0, PPDCH #1, . .. ), so that PSDCHs can be assigned to specific PPDCHs.

The exact physical resources allocated to a PPDCH may be specified viathe following example sets of quantities:

FFT size and cyclic prefix length, which determine the length of eachOFDM symbol within the PPDCH; Physical resources allocated to the PPDCHin the time dimension; and Physical resources allocated to the PPDCH inthe frequency dimension.

Specifying PPDCH Physical Resources in the Time Dimension

In the time dimension, a specific PPDCH may be defined via the followingexample quantities:

Total number of OFDM symbols assigned to this PPDCH; Absolute OFDMsymbol starting position within the PFDCH for this PPDCH (indexingbegins at 0); OFDM symbol cluster periodicity for this PPDCH; and Numberof consecutive OFDM symbols assigned per OFDM symbol cluster for thisPPDCH.

There is no requirement that the total number of OFDM symbols assignedto a given PPDCH be an integer multiple of the number of consecutiveOFDM symbols assigned per OFDM symbol cluster period for this PPDCH.

As an illustrative example, Table 4 shows example parameter settingsthat correspond to the example payload partitioning shown in FIGS. 3Aand 3B, where there are three equally-sized (in the time dimension)PPDCHs. Here, there is a strict time division between the three PPDCHs.As a result, the PFDCH contains a total of 440+232+60=732 OFDM symbolsin this example. In particular: PPDCH #0 contains OFDM symbols 0 through439, each of length 9216 samples; PPDCH #1 contains OFDM symbols 440through 671, each of length 17408 samples; and PPDCH #2 contains OFDMsymbols 672 through 731, each of length 66560 samples.

Note that there are also some additional excess samples in this example,which may be distributed to the cyclic prefixes of various OFDM symbols.

TABLE 4 Example PPDCH parameters (time dimension) for FIGS. 3A and 3BPPDCH PPDCH PPDCH Quantity #0 #1 #2 PPDCH length (seconds) 0.330 s 0.330s 0.330 s PPDCH length (samples) 4,055,040 4,055,040 4,055,040 FFT size8192 16384 65536 CP length (samples) 1024 1024 1024 OFDM symbol length9216 17408 66560 (samples) Total number of OFDM 440 232 60 symbolsAbsolute OFDM symbol 0 440 672 starting position OFDM symbol cluster 1 11 periodicity Number of consecutive 1 1 1 OFDM symbols per OFDM symbolcluster

In another illustrative example,—the frame structure shown in the lowerportion of FIG. 4. Table 5 shows example PPDCH parameters that mayresult in a frame structure illustrated in FIGS. 4A and 4B. In thisexample, the PFDCH contains a total of 754 OFDM symbols. In particular:

PPDCH #0 contains OFDM symbols 0-15, 26-41, 52-67, . . . , 728-743;PPDCH #1 contains OFDM symbols 16-23, 42-49, 68-75, . . . , 744-751; andPPDCH #2 contains OFDM symbols 24-25, 50-51, 76-77, . . . , 752-753.

TABLE 5 Example PPDCH parameters (time dimension) for FIGS. 4A and 4BPPDCH PPDCH PPDCH Quantity #0 #1 #2 FFT size 8192 16384 65536 CP length(samples) 1024 1024 1024 OFDM symbol length 9216 17408 66560 (samples)Total number of OFDM 464 232 58 symbols Absolute OFDM symbol 0 16 24starting position OFDM symbol cluster 26 26 26 periodicity Number ofconsecutive 16 8 2 OFDM symbols per OFDM symbol cluster

Note that there is no requirement that different PPDCHs have the sameOFDM symbol cluster periodicity, nor that multiple PPDCHs areidentically time-interleaved over their full lengths. For example, inTable 5, PPDCH #0 may be divided into two PPDCHs (#0A and #0B) that mayeither be interleaved with each other in a more macro sense. Table 6illustrates an example of such a configuration. In particular, PPDCH #0Acontains OFDM symbols 0-15, 52-67, 104-119, . . . , 672-687, 728-743;PPDCH #0B contains OFDM symbols 26-41, 78-93, 130-145, . . . , 646-661,702-717; PPDCH #1 contains OFDM symbols 16-23, 42-49, 68-75, . . . ,744-751; and PPDCH #2 contains OFDM symbols 24-25, 50-5, 76-77, . . . ,752-753.

Alternatively, the two PPDCHs may occupy approximately the first andsecond halves of the PFDCH, respectively. Table 7 illustrates an exampleof such a configuration. In particular: PPDCH #0A contains OFDM symbols0-15, 26-41, 52-67, . . . , 338-353, 364-379; PPDCH #0B contains OFDMsymbols 390-405, 416-431, . . . , 702-717, 728-743; PPDCH #1 containsOFDM symbols 16-23, 42-49, 68-75, . . . , 744-751; and PPDCH #2 containsOFDM symbols 24-25, 50-51, 76-77, . . . , 752-753.

TABLE 6 Additional example PPDCH parameters (time dimension) PPDCH PPDCHPPDCH PPDCH Quantity #0A #0B #1 #2 FFT size 8192 8192 16384 65536 CPlength (samples) 1024 1024 1024 1024 OFDM symbol 9216 9216 17408 66560length (samples) Total number of 240 224 232 58 OFDM symbols AbsoluteOFDM 0 26 16 24 symbol starting position OFDM symbol 52 52 26 26 clusterperiodicity Number of 16 16 8 2 consecutive OFDM symbols per OFDM symbolcluster

TABLE 7 Additional example PPDCH parameters (time dimension) PPDCH PPDCHPPDCH PPDCH Quantity #0A #0B #1 #2 FFT size 8192 8192 16384 65536 CPlength (samples) 1024 1024 1024 1024 OFDM symbol 9216 9216 17408 66560length (samples) Total number of 240 224 232 58 OFDM symbols AbsoluteOFDM 0 390 16 24 symbol starting position OFDM symbol 26 26 26 26cluster periodicity Number of 16 16 8 2 consecutive OFDM symbols perOFDM symbol clusterSpecifying PPDCH Physical Resources in the Frequency Dimension

The subcarriers within each OFDM symbol can be divided into useful andnon-useful subcarriers. Useful subcarriers lie within the systembandwidth minus a guard band, with the exception of the DC subcarrierwhich is a non-useful subcarrier. Non-useful subcarriers lie outside thesystem bandwidth minus the guard band.

The exact number of useful subcarriers is a function of the FFT size andsampling frequency, which together determine the subcarrier spacing, andthe system bandwidth.

FIG. 8 illustrates additional details relating to useful and non-usefulsubcarriers. Within the full IFFT/FFT range (size) 702, the usefulsubcarriers 704 are those which lie within the system bandwidth 706minus a guard band, with the exception of the DC subcarrier 708.Non-useful subcarriers 710 lie outside the system bandwidth minus theguard band.

There is no requirement that all useful subcarriers in an OFDM symbol beexplicitly assigned to a PPDCH. Note that each useful resource elementcan only be assigned to a maximum of one PPDCH. Any useful resourceelements that are not associated with a PPDCH may be assigned a value of0. Non-useful subcarriers may also be assigned a value of 0.

In the frequency dimension, a specific PPDCH may be defined via thespecific quantities. For example, a specific PPDCH may defined by anumber of useful subcarriers belonging to this PPDCH. This quantity mustbe less than or equal to the total number of all useful subcarriers perOFDM symbol. This specifies the actual size of the PPDCH in thefrequency dimension. It should be appreciated that the DC subcarrier isnot considered to be a useful subcarrier, so if the DC subcarrierhappens to lie within a particular PPDCH, then that subcarrier is notcounted against the number of useful subcarriers belonging to thatPPDCH. In one example a specific PPDCH may defined by an absolute indexof the first subcarrier belonging to this PPDCH. Subcarriers may beindexed beginning at 0 and proceeding sequentially upwards to the totalnumber of subcarriers minus 1 (i.e. the FFT size minus 1). Subcarrier 0is therefore essentially the lowest frequency subcarrier.

Multiple PPDCHs may be multiplexed beside each other in the frequencydimension. However, there is no actual interleaving of PPDCHs in thefrequency dimension. That is, in the frequency dimension, each PPDCHoccupies a contiguous set of physical subcarriers.

FIG. 9 shows an example of two PPDCHs 802 and 804 that have beenmultiplexed beside each other in the frequency dimension. Approximately⅔ of the useful subcarriers have been allocated to PPDCH #0 802, withthe remaining ⅓ of the useful subcarriers being allocated to PPDCH #1804. Table 8 contains the corresponding PPDCH parameters in thefrequency dimensions for the two example PPDCHs 802 and 804 shown inFIG. 9. In this example, both PPDCHs have been configured to use thesame FFT size and cyclic prefix length.

TABLE 8 Example PPDCH parameters (frequency dimension) for FIG. 9 PPDCHPPDCH Quantity #0 #1 FFT size 16384  16384  CP length (samples) 10241024 Subcarrier spacing 750 Hz 750 Hz System bandwidth 6 MHz 6 MHz Totalnumber of all useful 7600 7600 subcarriers Number of useful subcarriers5000 2600 assigned to this PPDCH Index of the first subcarrier 4392 9393belonging to this PPDCHPSDCH Mapping within a PPDCH

PSDCHs are mapped to virtual resources within their assigned PPDCH.Virtual resources are then mapped to logical resources within the samePPDCH, and then the logical resources of each PPDCH are mapped to actualphysical resources within the PFDCH. This process is described in detailin the following sections.

Logical Resources for a PPDCH

It has previously been described how a particular PPDCH is associatedwith corresponding physical resources. Regardless of what exact physicalresources belong to a PPDCH, the logical resources of a PPDCH can beconsidered to be contiguous in both the frequency and time dimensions,as illustrated in FIG. 10. Here, the logical subcarriers 904 of a PPDCH902 begin numbering at 0 at the left side of the diagram, which is thelowest frequency, and progress sequentially upwards to the right.Similarly, the logical OFDM symbols 906 of the PPDCH 902 begin numberingat 0 at the top of the diagram, which is earliest time, and progresssequentially upwards moving forward through time, toward the bottom ofthe diagram.

FIG. 11 introduces additional logical resource concepts for the contentsof a PPDCH. A stripe is a set of resources measuring one subcarrier inthe frequency dimension and running for the full time duration of thePPDCH, or all of the OFDM symbols, in the time dimension. Stripes aregrouped together in the frequency dimension into subbands, where thesubband width of each subband in the frequency dimension is equal to thenumber of stripes specified for the PPDCH. Each logical subband iscomposed of a number of logical stripes as illustrated in the diagram,which shows four logical subbands 1004, 1006, 1008 and 1010, eachcomposed of ten logical stripes. A particular stripe 1002 within thePPDCH's logical resources can be referenced via the logical subbandindex 1006 and the logical stripe index 1002 within that logical subband1006. As shown in FIG. 11, logical subcarriers may begin with the lowestfrequency subcarrier at the left and progress upwards in frequency whilemoving towards the right. Logical subbands may be indexed beginning with0 and progress sequentially upwards with frequency.

There is a constraint that the number of useful subcarriers assigned toa PPDCH must be an integer multiple of the subband-width for that samePPDCH, so that each PPDCH will always contain an integer number ofsubbands. However, there is no requirement that PPDCH assignments beginwith subband 0 or end with subband N−1. In one example, the system mightelectively depopulate subbands at the band edges to facilitate spectrumsharing or otherwise constrain out-of-band emissions relative to aprescribed spectral mask.

Virtual Resources for a PPDCH

Corresponding to each logical subband containing a number of logicalstripes is an equally-sized virtual subband containing the same numberof virtual stripes. Within each subband, there exists a one-to-onemapping of virtual stripes to logical stripes on a per OFDM symbolbasis. This may be considered to be conceptually equivalent to shufflingthe virtual stripes in order to obtain the logical stripes. A virtualsubband has the same index as the corresponding logical subband.

FIG. 12 illustrates an example of a mapping of virtual stripes belongingto a virtual subband to logical stripes belonging to a logical subband.Here, each subband has a width of ten stripes (W_(SB)=10). The tenvirtual stripes 1106 belonging to the virtual subband 1102 at the tophave a one-to-one stripe mapping 1108 to the ten logical stripes 1110belonging to the logical subband 1104 at the bottom. The stripe mapping1108 is dependent on the current logical OFDM symbol index 1112, and maytherefore vary from one logical OFDM symbol to the next.

Table 9 contains an example virtual-to-logical stripe mapping, withTable 10 containing the corresponding example logical-to-virtual stripemapping. It should be appreciated that the stripe mapping may vary as afunction of the logical OFDM symbol index and has a periodicity ofP_(SM)=10 in the time dimension in this example. Without loss ofgenerality, it may be assumed that virtual stripe #0 is always reservedfor a reference symbol or pilot symbol. In Table 10, the logical stripesthat contain reference symbols (i.e. which map to virtual stripe #0)have been highlighted with boldface text to show the reference symbolpattern being used in this example. In this example, the referencesymbol pattern repeats every five logical OFDM symbols, while the datastripe mapping pattern repeats every ten logical OFDM symbols.

In Table 9, the logical OFDM symbol index, or the row index, and thevirtual stripe index, or the column index, may be used to determine thetable entry that corresponds to the logical stripe index for thatparticular pair of logical OFDM symbol and virtual stripe indices.Conversely, in Table 10, the logical OFDM symbol index, or the rowindex, and the logical stripe index, or the column index, may be used todetermine the table entry that corresponds to the virtual stripe indexfor that particular pair of logical OFDM symbol and logical stripeindices.

TABLE 9 Example virtual stripe to logical stripe mapping Logical OFDMVirtual stripe index symbol index mod 10 0 1 2 3 4 5 6 7 8 9 0 0 2 3 4 56 7 8 9 1 1 4 8 9 0 1 2 3 5 6 7 2 8 4 5 6 7 9 0 1 2 3 3 2 0 1 3 4 5 6 78 9 4 6 7 8 9 0 1 2 3 4 5 5 0 3 4 5 6 7 8 9 1 2 6 4 9 0 1 2 3 5 6 7 8 78 5 6 7 9 0 1 2 3 4 8 2 1 3 4 5 6 7 8 9 0 9 6 8 9 0 1 2 3 4 5 7

TABLE 10 Example logical stripe to virtual stripe mapping Logical OFDMsymbol Logical stripe index index mod 10 0 1 2 3 4 5 6 7 8 9 0 0 9 1 2 34 5 6 7 8 1 3 4 5 6 0 7 8 9 1 2 2 6 7 8 9 1 2 3 4 0 5 3 1 2 0 3 4 5 6 78 9 4 4 5 6 7 8 9 0 1 2 3 5 0 8 9 1 2 3 4 5 6 7 6 2 3 4 5 0 6 7 8 9 1 75 6 7 8 9 1 2 3 0 4 8 9 1 0 2 3 4 5 6 7 8 9 3 4 5 6 7 8 0 9 1 2

In one example, the set of parameters for each PPDCH include one or morequantities. For example, the set of parameters may include a subbandwidth in the frequency dimension, which may be in units of stripes orsubcarriers. In one example, the set of parameters may further includestripe mapping periodicity in the time dimension, which may be in unitsof logical OFDM symbols. It should be appreciated that the number oflogical OFDM symbols in a PPDCH is not required to be an integermultiple of the stripe mapping periodicity. In one example, the set ofparameters may further include stripe mapping, which may be in the formof a table with the number of columns equal to the subband width and thenumber of rows equal to the stripe mapping periodicity. Alternatively, amore compact form of signaling the stripe mapping such as described inthe following section may be used.

It should be appreciated that the concept of virtual OFDM symbols is notdefined since virtual OFDM symbols are essentially directly equivalentto logical OFDM symbols. For example, virtual OFDM symbol #N is the sameas logical OFDM symbol #N.

Compact Signaling of Logical-to-Virtual Stripe Mapping

In one example, signaling a complete logical-to-virtual stripe mappingover the air may result in an inefficient use of limited wirelessresources due to the potential size of the stripe mapping table thatmust be transmitted for each PPDCH. Thus, an example a more compact formof signaling the stripe mapping to be used to the receiver is described.This compact signaling then allows the full logical to virtual stripemapping table to be constructed at the receiver for each PPDCH.

Two desirable requirements for a good virtual↔logical stripe mapping areas follows. First, the stripe mapping should support the ability to havescattered reference symbols. For example, the stripe mapping shouldsupport the ability to map reference symbols to different logicalstripes in different logical OFDM symbols. Second, the stripe mappingshould vary the virtual data stripes that get mapped to the logicalstripes adjacent to the reference symbol to avoid some virtual datastripes consistently having better channel estimates than other virtualdata stripes.

In one example, a stripe mapping algorithm for each PPDCH may include anumber of quantities, which would reduce the amount of informationneeding to be signaled over the air. For example, stripe mappingperiodicity (P_(SM)) may be the same quantity as has previously beendefined. A vector of reference symbol logical stripe mapping positions(L_(RS)(k)) may have a length equal to the stripe mapping periodicity.For each OFDM symbol k (modulo P_(SM)), this would specify the logicalstripe to which virtual stripe 0 (which contains reference symbols)maps. This allows the reference symbol position to be varied on an OFDMsymbol by symbol basis. A vector of stripe rotation may have values withlength equal to the stripe mapping periodicity. For each OFDM symbol k(modulo P_(SM)). This would specify the “rotation” to be applied toeither: the virtual stripes other than virtual stripe 0, or all of thevirtual stripes that carry data rather than a reference symbol, in orderto obtain logical stripe indices. This quantity may be labelledR_(VL)(k); or the logical stripes other than the logical stripeL_(RS)(k) which carries the reference symbol, or all of the logicalstripes that carry data rather than a reference symbol, in order toobtain virtual stripe indices. This quantity may be labelled R_(LV)(k).

Table 11 contains the compact form of specifying the stripe mapping forthe example corresponding to Table 9 and Table 10. Recall that for thisexample, the stripe mapping periodicity is P_(SM)=10, and the width ofthe subband is W_(SB)=10. In addition, the relation between the virtualto logical and logical to virtual stripe rotations can be expressed as:R _(VL)(k)+R _(LV)(k)=W _(SB)−1.  equ. (5)

TABLE 11 Example compact form for signaling of stripe mapping dataLogical Logical Virtual to Logical to OFDM symbol stripe for logicalstripe virtual stripe index mod 10 reference symbol rotation for datarotation for data (k) (L_(RS)(k)) (R_(VL)(k)) (R_(LV)(k)) 0 0 1 8 1 4 72 2 8 3 6 3 2 9 0 4 6 6 3 5 0 2 7 6 4 8 1 7 8 4 5 8 2 0 9 9 6 7 2

FIG. 13 illustrates a conceptual view of how the virtual to logicalstripe rotation works. This example corresponds to modulo logical OFDMsymbol k=6 from Table 11. As can be seen, the reference symbol onvirtual stripe 0 1202 is mapped straight through to logical stripeL_(RS)(k)=4 1204. A rotation (modulo W_(SB)=10) of R_(VL)(k)=8 isapplied to the data virtual stripes 1206. These rotated data virtualstripes 1208 are then mapped essentially straight through to theavailable logical stripes 1210, which include all of the logical stripeswith the exception of logical stripe #4 1204 which is already occupiedby the reference symbol.

FIG. 14 shows the corresponding logical to virtual stripe rotation andmapping for modulo logical OFDM symbol k=6 from Table 11. Here, thelogical stripe carrying the reference symbol L_(RS)(k)=4 1302 isextracted and mapped onto virtual stripe #0 1304. A rotation moduloW_(SB)=10 of R_(LV)(k)=1 is applied to the data logical stripes 1308,and then these rotated data logical stripes 1310 are mapped straightthrough onto the data virtual stripes 1312 #1 through #9.

Let k represent the logical OFDM symbol index modulo the stripe mappingperiodicity (P_(SM)), which equals 10 in this example. At thetransmitter, a reference symbol for modulo symbol k is mapped fromvirtual stripe index 0 to the corresponding logical stripe indexL_(RS)(k) (0≤L_(RS)(k)<W_(SB)) given in the table.S _(L)(k,L _(RS)(k))=S _(V)(k,0)  equ. (6)At the receiver, this process is reversed, and a reference symbol formodulo symbol k is mapped from the corresponding logical stripe indexL_(RS)(k) given in the table back to virtual stripe index 0.S _(V)(k,0)=S _(L)(k,L _(RS)(k))  equ. (7)For virtual to logical data stripe mapping at the transmitter, thefollowing example procedure can be followed. Let S_(V) (k,i)(0<S_(V)(k,i)<W_(SB)) and S_(L)(k,i) (0≤S_(L)(k,i)<W_(SB) andS_(L)(k,i)≠L_(RS)(k)) represent a corresponding pair of virtual andlogical stripe indices that map to each other for modulo symbol k(0≤k<P_(SM)). Let R_(VL)(k) (0≤R_(VL)(k)<W_(SB) andR_(VL)(k)≠(L_(RS)(k)+W_(SB)−1) mod W_(SB)) represent the virtual tological stripe rotation for data for modulo symbol k. The logical datastripe index S_(L) (k,i) corresponding to a particular virtual datastripe index S_(V) (k,i) (0<i<W_(SB)) can then be calculated as follows,noting that for a valid stripe mapping R_(VL)(k)≠(L_(RS)(k)+W_(SB)−1)mod W_(SB) implies that R_(VL)(k)+1≠L_(RS)(k) for all k.

$\begin{matrix}{{\overset{\sim}{L}(k)} = \left\{ {{\begin{matrix}{L_{RS}(k)} & {{{{if}\mspace{14mu}{R_{VL}(k)}} + 1} < {L_{RS}(k)}} \\{{L_{RS}(k)} + W_{SB}} & {{{{if}\mspace{14mu}{R_{VL}(k)}} + 1} > {L_{RS}(k)}}\end{matrix}i} = {{1\mspace{14mu}\ldots\mspace{14mu} W_{SB}} - 1}} \right.} & {{equ}.\mspace{14mu}(8)} \\{{S_{V}\left( {k,i} \right)} = i} & {{equ}.\mspace{14mu}(9)} \\{{\overset{\sim}{S}\left( {k,i} \right)} = {{S_{V}\left( {k,i} \right)} + {R_{VL}(k)}}} & {{equ}.\mspace{14mu}(10)} \\{{S_{L}\left( {k,i} \right)} = \left\{ \begin{matrix}{{\overset{\sim}{S}\left( {k,i} \right)}\;{{mod}W}_{SB}} & {{{if}\mspace{14mu}{\overset{\sim}{S}\left( {k,i} \right)}} < {\overset{\sim}{L}(k)}} \\{\left( {{\overset{\sim}{S}\left( {k,i} \right)} + 1} \right){{mod}W}_{SB}} & {{{if}\mspace{14mu}{\overset{\sim}{S}\left( {k,i} \right)}} \geq {\overset{\sim}{L}(k)}}\end{matrix} \right.} & {{equ}.\mspace{14mu}(11)}\end{matrix}$

At the receiver, the virtual data stripe index S_(V) (k,i) correspondingto a particular logical data stripe index S_(L)(k,i) (0≤i<W_(SB) andi≠L_(RS)(k)) can then be calculated as shown below.R_(LV)(k)=W_(SB)−R_(VL)(k)−1 represents the virtual to logical striperotation for data for modulo symbol k.

$\begin{matrix}{{{x(k)} = {W_{SB} - {R_{LV}(k)}}}{i = {{{0\mspace{14mu}\ldots\mspace{14mu} W_{SB}} - {1\mspace{14mu}{and}\mspace{14mu} i}} = {L_{RS}(k)}}}} & {{equ}.\mspace{14mu}(12)} \\{{S_{L}\left( {k,i} \right)} = i} & {{equ}.\mspace{14mu}(13)}\end{matrix}$If x(k)<L_(RS)(k):

$\begin{matrix}{{S_{V}\left( {k,i} \right)} = \left\{ \begin{matrix}{\left( {{S_{L}\left( {k,i} \right)} + {R_{LV}(k)}} \right){{mod}W}_{SB}} & \begin{matrix}{{{if}\mspace{14mu}{S_{L}\left( {k,i} \right)}} < {{x(k)}\mspace{14mu}{or}}} \\{{S_{L}\left( {k,i} \right)} > {L_{RS}(k)}}\end{matrix} \\{\left( {{S_{L}\left( {k,i} \right)} + {R_{LV}(k)} + 1} \right){{mod}W}_{SB}} & {{{if}\mspace{14mu}{x(k)}} \leq {S_{L}\left( {k,i} \right)} < {L_{RS}(k)}}\end{matrix} \right.} & {{equ}.\mspace{14mu}(14)}\end{matrix}$Conversely, if x(k)≥L_(RS)(k):

$\begin{matrix}{{S_{V}\left( {k,i} \right)} = \left\{ \begin{matrix}{\left( {{S_{L}\left( {k,i} \right)} + {R_{LV}(k)}} \right){{mod}W}_{SB}} & {{{if}\mspace{11mu}{L_{RS}(k)}} < \;{S_{L}\left( {k,i} \right)} < {x(k)}} \\{\left( {{S_{L}\left( {k,i} \right)} + {R_{LV}(k)} + 1} \right){{mod}W}_{SB}} & {\mspace{11mu}\begin{matrix}{{{if}\mspace{14mu}{S_{L}\left( {k,i} \right)}} > {{L_{RS}(k)}\mspace{14mu}{or}}} \\{{S_{L}\left( {k,i} \right)} \geq {x(k)}}\end{matrix}}\end{matrix} \right.} & {{equ}.\mspace{14mu}(15)}\end{matrix}$

Table 12 summarizes the list of parameters that need to be provided foreach PPDCH within the PFDCH.

TABLE 12 Summary of parameters required for each PPDCH ParameterCategory Parameter General PPDCH index (may be implicitly signaled byposition within a list of PPDCHs) FFT size Cyclic prefix length (insamples) Time Total number of OFDM symbols assigned to this PPDCHdimension Absolute OFDM symbol starting position within the PFDCH forthis PPDCH OFDM symbol cluster periodicity for this PPDCH Number ofconsecutive OFDM symbols assigned per OFDM symbol cluster for this PPDCHFrequency Number of useful subcarriers assigned to this PPDCH (mustdimension be an integer multiple of the subband width further below)Absolute index of the first subcarrier belonging to this PPDCH StripeSubband width in the frequency dimension (in units of mapping stripes orsubcarriers) Stripe mapping periodicity in the time dimension (in unitsof logical OFDM symbols) Virtual↔Logical stripe mapping table or compactstripe mapping signaling formatMapping a PSDCH to Virtual Resources

Virtual stripe #0 may always be reserved for reference symbols. Thisdoes not result in any loss of generality since virtual stripe #0 may bemapped to any desired logical stripe.

The reference symbol density may easily be calculated as the reciprocalof the subband width. In the examples given above with a subband widthof 10, the reference symbol density is 10%. Conversely, a desiredreference symbol density can also be used to obtain the appropriatesubband width to configure.

A subband block is defined as a set of resource elements measuring onesubband in the frequency dimension by one OFDM symbol in the timedimension. Resources may be allocated to a PSDCH in units of subbandblocks, where a subset of the virtual stripes within each virtualsubband may be assigned to a particular PSDCH.

Virtual resources may be assigned to a PSDCH via the followingparameters: Total number of subband blocks allocated to this PSDCH;subband index of the first subband block allocated to this PSDCH;subband cluster size or the number of consecutive subband blocks persubband cluster period allocated to this PSDCH; the first subband for alogical OFDM symbol is considered to be consecutive to the last subbandfor the preceding logical OFDM symbol; subband cluster periodicity forthis PSDCH which specifies the periodicity of successive subbandclusters that are allocated to this PSDCH; index of the first allocatedvirtual stripe within a virtual subband for this PSDCH; strip clustersize or the number of consecutive allocated virtual stripes within avirtual subband for this PSDCH; index of the first logical OFDM symboloccupied by this PSDCH; logical OFDM symbol cluster size or the numberof consecutive logical OFDM symbols per logical OFDM symbol clusteroccupied by this PSDCH; and logical OFDM symbol cluster periodicity forthis PSDCH.

It should be appreciated that the total number of resource elementsallocated to a PSDCH may be obtained by multiplying the total number ofallocated subband blocks by the number of consecutive allocated virtualstripes within a virtual subband.

FIG. 15 illustrates how the above parameters can be used to map a PSDCHonto a set of virtual resources within a PPDCH. Table 13 contains theparameters that correspond to the example PSDCH mapping shown in FIG.15. In this example, the total number of resource elements allocated tothis PSDCH is equal to 16, or the total number of allocated subbandblocks, multiplied by 4, or the number of consecutive allocated virtualstripes within a virtual subband, which equals 64. In the diagram, mostbut not all of the subband clusters 1402 have been circled to show whichsubbands belong to which subband clusters.

TABLE 13 Example PSDCH virtual resource mapping parameters ParameterValue Total number of allocated subband blocks 16 Subband index of firstsubband block 1 Subband cluster size 2 Number of consecutive subbandblocks per subband cluster period Subband cluster periodicity 3 Index offirst allocated virtual stripe within a virtual subband 6 Stripe clustersize 4 Number of consecutive allocated virtual stripes within a virtualsubband Index of first occupied logical OFDM symbol 4 Logical OFDMsymbol cluster size 3 Number of consecutive logical OFDM symbols perOFDM symbol period Logical OFDM symbol cluster periodicity 8

Within a virtual resource mapping for a PSDCH, modulation symbols may bemapped to resource elements beginning with the first allocated virtualstripe of the first allocated subband block of the first occupiedlogical OFDM symbol, and progressing by virtual stripe within eachsubband block, then by subband block within the same logical OFDMsymbol, and finally by logical OFDM symbol.

In the above example, modulation symbols will be mapped to virtualstripes 6/7/8/9 of virtual subband 1 and logical OFDM symbol 4, then tovirtual stripes 6/7/8/9 of virtual subband 2 and logical OFDM symbol 4,then to virtual stripes 6/7/8/9 of virtual subband 0 and OFDM symbol 5,then to virtual stripes 6/7/8/9 of virtual subband 1 and OFDM symbol 5,and so on until the total number of allocated subband blocks has beenprocessed.

Frame Content Description Provided to the Receiver

In one example, information about the payload content formatting of eachframe, including information on the encoding, FFT sizes, etc, isprovided to the receiver to facilitate the receiver processing anddecoding of the payload contents. There are a variety of methods thatmay be used to communicate this formatting information to the receiver.For example, the payload content descriptions could be signaled withineach frame in one of the non-payload regions shown in FIG. 2.Alternatively, if the payload content structure varies more slowly thanon a frame-by-frame basis, then the payload content descriptions couldbe signaled on an as-required basis.

In one example, the receiver is provided with the number of distinctPPDCHs in the frame and the number of PSDCHs in the frame. For eachPPDCH, the receiver is further provided with physical resourcesallocated to that PPDCH, FFT size, and cyclic prefix length. Thephysical resources allocated to that PPDCH may include the number ofOFDM symbols allocated to that PPDCH, as well as which particularsymbols are allocated to that PPDCH. It should be appreciated thatdistinct PPDCHs may be interleaved with each other. For each PSDCH, thereceiver is further provided with service associated with that PSDCH,physical resources allocated to that PSDCH, modulation used for thatPSDCH, and transport block size in bytes. The service associated withthat PSDCH may be thought of as the data stream flow to which aparticular PSDCH belongs. For example, a specific television program maybe considered to be a particular service.

Table 14, Table 15, and Table 16, respectively, provide more detaileddescriptions of the parameter fields that may be provided to thereceiver. One PFDCH descriptor, listed in Table 14, may be required foreach frame. One PPDCH descriptor, listed in Table 15, may be requiredfor each PPDCH contained in the frame. One PSDCH descriptor, listed inTable 16, may be required for each PSDCH contained in the frame.

TABLE 14 PFDCH descriptor Field description Number of PPDCHs

TABLE 15 PPDCH descriptor Field description FFT size (e.g. 2048, 4096,8192, 16384, 32768, 65536) Cyclic prefix length Total number of OFDMsymbols in this PPDCH Absolute OFDM symbol starting position for thisPPDCH OFDM symbol cluster periodicity OFDM symbol cluster size (Numberof consecutive OFDM symbols per OFDM symbol cluster) Number of usefulsubcarriers for this PPDCH Absolute index of the first subcarrierbelonging to this PPDCH Subband width (Note that the number of usefulsubcarriers belonging to the PPDCH must be an integer multiple of thesubband width) Stripe mapping periodicity in the time dimensionLogical-to-virtual stripe mapping table or Compact stripe mappingparameters Number of PSDCHs in the PPDCH

TABLE 16 PSDCH descriptor Field description Service associated with thisPSDCH Transport block size FEC coding type (e.g. Turbo, Low DensityParity Check (LDPC)) Modulation level (e.g. QPSK, 16QAM, 64QAM, 256QAM)Total number of subband blocks for this PSDCH Subband index of the firstsubband block for this PSDCH Subband cluster size for this PSDCH Subbandcluster periodicity for this PSDCH Index of the first allocated virtualstripe within a virtual subband for this PSDCH Number of consecutiveallocated virtual stripes within a virtual subband for this PSDCH Indexof the first logical OFDM symbol occupied by this PSDCH Logical OFDMsymbol cluster size (Number of consecutive logical OFDM symbols per OFDMsymbol period occupied by this PSDCH) Logical OFDM symbol clusterperiodicity for this PSDCH

FIG. 16 shows an example of how all of the various descriptors may becommunicated to the receiver. In this example, the single PFDCHdescriptor 1502 per frame occurs first, immediately followed by all ofthe concatenated PPDCH descriptors 1504. This frame, for example,contains n+1 PPDCHs. This is then followed by all of the concatenatedPSDCH descriptors 1506. In this frame, for example, PPDCH #0 has p+1PSDCHs and PPDCH #n has q+1 PSDCHs.

The ordering of the descriptors shown in FIG. 16 can easily berearranged if so desired. For example, the PSDCH descriptors associatedwith a particular PPDCH may follow immediately after the descriptor forthat PPDCH, instead of all being concatenated together following thegroup of concatenated PPDCH descriptors.

In one set of embodiments, a method 1700 for constructing andtransmitting a frame may include the actions shown in FIG. 17. Themethod 1700 may also include any subset of the features, elements andembodiments previously described. The method 1700 may be implemented bya base station or an access point, for example.

At step 1710, digital circuitry of the base station may performoperations, wherein the operations include constructing a payload regionof the frame, wherein the payload region includes a plurality ofpartitions, wherein each of the partitions includes a correspondingplurality of OFDM symbols, wherein each partition has a correspondingFFT size and a corresponding cyclic prefix size for OFDM symbols in thatpartition.

At step 1720, a transmitter of the base station may transmit the frameover a wireless channel.

In some embodiments, the operations also include embedding signalinginformation in a non-payload region of the frame, e.g., as variouslydescribed above. The signaling information indicates the FFT size andthe cyclic prefix size for each of the partitions. In other embodiments,the signaling information may be embedded elsewhere, e.g., in a previousframe.

In some embodiments, each of the partitions includes a corresponding setof overhead resource elements, such as reference symbols. In theseembodiments, the above-described operations may also include schedulingsymbol data from one or more service data streams to each of thepartitions after having reserved the overhead resource elements withinthe frame.

Different partitions may have different values of FFT size, and thus,different values of subcarrier spacing. For example, the subcarrierspacing for any given partition is the ratio of sample rate to the FFTsize for that partition. Consequently, the different partitions willhave different amounts of Doppler tolerance, or tolerance to Dopplershift due to motion of user devices. For example, a first of thepartitions may be targeted for transmission to mobile devices, while asecond of the partitions is targeted for transmission to fixed devices.Thus, the FFT size corresponding to the first partition is configured tobe smaller than the FFT size corresponding to the second partition. Thisallows the first partition to have larger subcarrier spacing, and thus,greater tolerance to the frequency shift of subcarriers due to motion ofthe mobile devices.

Furthermore, different partitions may have different cyclic prefixsizes, or guard interval durations, and thus, be able to toleratedifferent amounts of delay spread. For example, a first of thepartitions may be targeted for transmission to a first set of userdevices that are expected to have large delay spreads, while a second ofthe partitions is targeted for transmission to a second set of userdevices that are expected to have smaller delay spreads. Thus, thecyclic prefix size for the first partition is configured to be largerthan the cyclic prefix size for the second partition.

A given user device may receive the transmitted frame using a wirelessreceiver, and extract the OFDM symbols from the partition to which theuser device has been assigned. The OFDM symbols are decoded to obtaindigital information signals, which are then displayed or otherwiseoutputted to a user. The base station may signal to each user device oreach type of user device the partition to which it is assigned. The basestation may also signal the type of service carried in each partition.The partition may include one or more service data streams, as variouslydescribed herein. In the case that the partition includes more than oneservice data stream, the user device may extract OFDM symbols from oneor more of the service data streams for which it has been grantedpermission to access. The base station may signal to the user devicewhich service data streams it is permitted to access, for example, basedon permission control information provided by the broadcast gateway.

In one set of embodiments, a method 1800 for constructing andtransmitting a frame having a specified temporal length may include theactions shown in FIG. 18. The method 1800 may also include any subset ofthe features, elements and embodiments previously described. The method1800 may be implemented by a base station or access point, for example,and may enable flexibility in configuring transmissions from the basestation.

At step 1810, digital circuitry of the base station may performoperations, where the operations include steps 1815 through 1830, asfollows.

At step 1815, for each of one or more partitions of the frame, thedigital circuitry may determine a corresponding OFDM symbol length forOFDM symbols belonging to the partition, wherein the OFDM symbol lengthis based on a corresponding FFT size and a corresponding cyclic prefixsize, wherein the corresponding cyclic prefix size satisfies a sizeconstraint based on a corresponding minimum guard interval duration.

At step 1820, the digital circuitry may compute a sum of OFDM symbollengths, in terms of samples, in a union of the OFDM symbols over thepartitions.

At step 1825, the digital circuitry may compute a number of excesssamples based on the sum and a length, in term of samples, of a payloadregion of the frame.

At step 1830, the digital circuitry may construct the frame. The actionof constructing the frame may include, for example, for each OFDM symbolin the union, assigning the OFDM symbol to exactly one of at least onesubset of the union using at least one of the number of excess samplesand an index of the OFDM symbol, and adding a number to the cyclicprefix size of each OFDM symbol in each of the at least one subset ofthe union, prior to embedding the OFDM symbols in the frame, wherein aunique number is used for each of the at least one subset of the union.

Each OFDM symbol belongs to one and only one of the subsets. In otherwords, the intersection of any two subsets is null, and the union of allof the subsets is the union of all of the OFDM symbols in the frame.

In some cases, the excess samples may divide evenly between theavailable OFDM symbols, so that there is only one subset which is equalto the full union. In other embodiments, the excess samples may bedistributed to two or more subsets of OFDM symbols.

As previously described, at least one of the number of excess samplesand an index of the OFDM symbol is used to determine into which subset aparticular OFDM symbol shall be placed. In some embodiments, only one ofthe two quantities is used.

In one example, for a particular subset, the cyclic prefixes of all ofthe OFDM symbols in that subset may be incremented by the same number.Different subsets may use different numbers.

At step 1835, a transmitter of the base station may transmit the frameover a wireless channel.

In some embodiments, the action of constructing the frame may alsoinclude, for one of the at least one subset of the union, setting theunique number for that subset to zero.

In some embodiments, one of the at least one subset of the unionrepresents an initial contiguous subset of the OFDM symbols in theunion.

In some embodiments, the at least one subset of the union and the uniquenumber for each of the at least one subset of the union are determinedaccording to an algorithm known to remote devices that receive saidtransmissions.

A remote device uses knowledge of the subset along with otherinformation, such as the frame start, the length of the preamble insymbols, the start of the payload region, the configured FFT sizes andcyclic prefix lengths, and PFDCH length, to determine exactly the groupof samples in the received frame that corresponds to each OFDM symbol inits assigned partition and assigned service data stream or streams.

In one set of embodiments, a method for constructing and transmitting aframe having a specified temporal length may be implemented as follows.It should be appreciated that the method may enable flexibility inconfiguring transmissions from a base station. The method may includeperforming operations using digital circuitry of the base station,wherein said operations include: (a) computing a sum of sample lengthsof OFDM symbols assigned to a payload region of a frame; (b) computing anumber of excess samples based on the sum and a sample length of thepayload region; and (c) constructing the frame, where the action ofconstructing the frame includes distributing the excess samples to oneor more cyclic prefixes of one or more of the OFDM symbols assigned tothe frame. The frame may be transmitted onto a wireless channel using atransmitter of the base station.

In one set of embodiments, a method 1900 for constructing andtransmitting a frame may include the actions shown in FIG. 19. Themethod 1900 may also include any subset of the features, elements andembodiments previously described. The method 1900 may be implemented bya base station or access point, for example.

At step 1910, digital circuitry of the base station may performoperations, wherein the operations include 1915 and 1920, as follows.

At step 1915, the digital circuitry may construct a plurality ofpartitions, wherein each of the partitions includes a corresponding setof OFDM symbols, wherein the OFDM symbols in each partition conform to acorresponding FFT size and satisfy a corresponding minimum guardinterval. In other words, for each partition, each OFDM symbol in thatpartition has a cyclic prefix that is greater than or equal to theminimum guard interval for that partition and has an FFT size equal tothe FFT size of that partition.

At step 1920, the digital circuitry may construct a frame by timeinterleaving the OFDM symbols of the partitions to form OFDM symbolclusters, as variously described above. Each of the OFDM symbol clustersbelongs to a corresponding one of the partitions. The OFDM symbolclusters may be defined by a specified value of OFDM symbol cluster sizefor each partition, and a specified value of OFDM symbol cluster periodfor each partition.

At step 1930, a transmitter of the base station may transmit the frameover a wireless channel.

In some embodiments, a first of the partitions may be targeted fortransmission to mobile devices, while a second of the partitions istargeted for transmission to fixed devices. Thus, the FFT sizecorresponding to the first partition is configured to be smaller thanthe FFT size corresponding to the second partition.

In some embodiments, the above-described operations also includeembedding signaling information in the frame, wherein the signalinginformation indicates the specified value of OFDM symbol cluster sizefor each partition and the specified value of OFDM symbol cluster periodfor each partition. A user device may be configured to receive theframe, and recover the signaling information from the frame. For aparticular partition to which the user device has been assigned, theuser device determines the corresponding specified values of OFDM symbolcluster size and OFDM symbol cluster period based on the signalinginformation in the frame. The user device may then recover the OFDMsymbols belonging to the OFDM symbol clusters of the particularpartition, using the corresponding specified values.

In one set of embodiments, a method 2000 for constructing andtransmitting a transport stream may include the actions shown in FIG.20, where the transport stream includes a frame. The method 2000 mayalso include any subset of the features, elements and embodimentspreviously described above. The method 2000 may be implemented by a basestation or access point, for example.

At step 2010, digital circuitry of the base station may performoperations, wherein the operations include 2015 and 2020, as follows.

At 2015, the digital circuitry may construct a payload region of theframe, wherein samples in the payload region correspond to a specifiedsample rate, wherein the specified sample rate is selected from auniverse of possible sample rates supported by transmission circuitry ofthe base station, wherein the samples in the payload regions are dividedinto one or more partitions, wherein each of the partitions includes acorresponding set of OFDM symbols.

At step 2020, the digital circuitry may embed signaling information inthe transport stream, wherein the signaling information includesinformation indicating the specified sample rate.

At step 2030, a transmitter of the base station may transmit thetransport stream over a wireless channel.

In some embodiments, the sample rate has been specified by an operatorof a broadcast network that includes said base station. The operator mayspecify the sample rate, for example, by accessing the broadcast gateway102 illustrated in FIG. 1A.

In some embodiments, the signaling information is embedded in anon-payload region of the frame.

In some embodiments, each partition has a corresponding value of FFTsize for OFDM symbols included in that partition.

In some embodiments, for each partition, the FFT size for the partitionand the sampling rate have been selected to define a subcarrier spacingfor the partition that satisfies a specified minimum subcarrier spacingor Doppler tolerance for that partition.

A given user device may wirelessly receive the transport stream,including the frame and the signalling information. The user device mayconfigure its OFDM receiver and/or analog-to-digital conversioncircuitry to use the sample rate specified by the signaling informationin order to capture samples of the payload region of the frame. The userdevice may then decode an appropriate partition and service data streamor streams of the frame as variously described.

Contrasts with DVB

Digital Video Broadcasting (“DVB”) and Second Generation TerrestrialDVB-T2 includes a Future Extension Frame (“FEF”) as the mechanism toenable a mixed Super Frame (“SF”) structure. According to DVB, the mixedSuper Frame permits with the same network to transmit in the samefrequency band both fixed and mobile TV services each with an optimizedwaveform such as time segmented transmission of T2 and FEF frames.

To preserve backward compatibility, DVB-T2 imposes several constraintsto allow the introduction of FEFs. For example, according to DVB-T2, theratio of T2 frames to FEFs is fixed and is repeated inside a SF. Inaddition, an SF must start with a T2-frame and should end with a FEF.Also, it is not possible to have 2 consecutive FEFs according to DVB-T2.

The present disclosure imposes no such constraints. In particular, theratio of transport resources allocated between FFT modes and respectivepartitions is determined statistically based on the respectiveconfiguration in each mode, including FFT size, CP duration, and payloadextent in symbols. In addition, there are no restrictions on the FFTmode inserted at either the start or end of a frame. Also, the FFT modeswill repeat in succession as needed to satisfy the statisticalmultiplexing arrangement.

One significant difference between the present disclosure and DVB-T2lies in the manner in which FFT modes are multiplexed. DVB-T2 with FEFoperates on the basis of frames distributed over the duration of a SF.Services are essentially multiplexed in time on individual frameboundaries separated by P1 preambles. The present disclosure, on theother hand, describes a scheduling arrangement that permits services tobe multiplexed on OFDM symbol boundaries within the same frame,providing substantial added flexibility. More than two modes can bemultiplexed in the same transport, providing multiple levels of mobilityvs. throughput efficiency. Time multiplexing on symbol boundariesincreases the extent of either mode, maximizing time diversity. Theframe configuration is signaled to the receiver, indicating theperiodicity of each FFT mode and the symbols needed to recover thepayload associated with either service.

The present disclosure further permits the option to separate partitionsin the frequency domain, thereby confining each partition to separatesets of subcarriers. This is a capability not readily addressable withinDVB.

Efforts to merge different FFT modes within a single DVB frame wouldrequire a change in the preamble structure, undermining backwardcompatibility with legacy receivers. Given the manner in which framesare multiplexed in DVB, confined to separate P1 preamble regions, thereis no gain in time diversity. Restrictions imposed on the ratio of T2 toFE frames limits the usefulness of this DVB multiplexing arrangement toa limited set of hand-crafted use case scenarios.

Any of the various embodiments described herein may be realized in anyof various forms, e.g., as a computer-implemented method, as acomputer-readable memory medium, as a computer system, etc. A system maybe realized by one or more custom-designed hardware devices such asApplication Specific Integrated Circuits (ASICs), by one or moreprogrammable hardware elements such as Field Programmable Gate Arrays(FPGAs), by one or more processors executing stored programinstructions, or by any combination of the foregoing.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of the methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a computer system may be configured to include aprocessor (or a set of processors) and a memory medium, where the memorymedium stores program instructions, where the processor is configured toread and execute the program instructions from the memory medium, wherethe program instructions are executable to implement any of the variousmethod embodiments described herein (or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets). Thecomputer system may be realized in any of various forms. For example,the computer system may be a personal computer (in any of its variousrealizations), a workstation, a computer on a card, anapplication-specific computer in a box, a server computer, a clientcomputer, a hand-held device, a mobile device, a wearable computer, asensing device, a television, a video acquisition device, a computerembedded in a living organism, etc. The computer system may include oneor more display devices. Any of the various computational resultsdisclosed herein may be displayed via a display device or otherwisepresented as output via a user interface device.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

The invention claimed is:
 1. A method, comprising: generating a dataframe; and wirelessly broadcasting the data frame, wherein generatingthe data frame comprises: generating a first set of orthogonal frequencydomain multiplexing (OFDM) symbols; and generating a second set of OFDMsymbols, wherein each OFDM symbol of the first set of OFDM symbols andthe second set of OFDM symbols comprises a useful portion and a cyclicprefix, and wherein generating said each OFDM symbol comprises:converting a block of frequency domain data to time-domain samples usingan inverse fast Fourier transform having a transform size to form theuseful portion; and forming the cyclic prefix by prepending to said eachOFDM symbol a plurality of time-domain samples from an end of the usefulportion of the OFDM symbol, wherein generating the data frame furthercomprises: forming the first set of OFDM symbols using a first transformsize and a first cyclic prefix size; and forming the second set of OFDMsymbols using a second transform size different than the first transformsize and a second cyclic prefix size, and wherein the data framecomprises a plurality of parameters separately indicating the firstcyclic prefix size, the second cyclic prefix size, the first transformsize, and the second transform size.
 2. The method of claim 1, whereinthe first cyclic prefix size is different than the second cyclic prefixsize.
 3. The method of claim 1, wherein the frequency domain datacomprises a set of useful subcarriers and a set of non-usefulsubcarriers; and wherein the data frame further comprises a secondplurality of parameters separately indicating a number of usefulsubcarriers in the first set of OFDM symbols and a number of usefulsubcarriers in the second set of OFDM symbols.
 4. A computer programproduct for transmitting a variable rate transport stream, the computerprogram product comprising one or more non-transitory computer-readablestorage devices having stored thereon computer executable instructionsthat when executed cause at least one processor to: construct a payloadregion of a data frame, wherein samples in the payload region correspondto a first sample rate, wherein the first sample rate is selected from aplurality of sample rates; divide the samples in the payload region intoone or more partitions, wherein each of the one or more partitionscomprises a corresponding set of orthogonal frequency domainmultiplexing (OFDM) symbols; embed signaling information in thetransport stream that includes the data frame, wherein the signalinginformation comprises data indicative of the first sample rate, and asecond sample rate different than the first sample rate is used for thesignaling information; and transmit the transport stream based at leastin part on the first sample rate.
 5. The computer program product ofclaim 4, wherein the computer executable instructions, when executed,further cause the at least one processor to receive data indicative ofthe first sample rate from an operator of a broadcast network.
 6. Thecomputer program product of claim 4, wherein the computer executableinstructions, when executed, further cause the at least one processor toembed the signaling information in a non-payload region of the dataframe.
 7. The computer program product of claim 4, wherein eachpartition of the one or more partitions has a corresponding value offast Fourier transform (FFT) size for OFDM symbols associated with theone or more partitions.
 8. The computer program product of claim 7,wherein the computer executable instructions, when executed, furthercause the at least one processor to, for each partition, select the FFTsize for the partition and the first sampling rate to define asubcarrier spacing for the partition that satisfies a specified minimumsubcarrier spacing for the partition.
 9. The computer program product ofclaim 4, wherein each partition of the one or more partitions has acorresponding value of cyclic prefix size for OFDM symbols associatedwith the one or more partitions.
 10. The computer program product ofclaim 9, wherein the cyclic prefix size corresponding to a partition ofthe one or more partitions is selected from a group consisting of: 192,384, 512, 768, 1024, 1536, 2048, 3072, and 4096 samples.
 11. Anapparatus, comprising: a processor configured to generate a data frame;and a transmitter configured to wirelessly broadcast the data frame,wherein the data frame comprises a first set of orthogonal frequencydomain multiplexing (OFDM) symbols and a second set of OFDM symbols,each OFDM symbol in the first set of OFDM symbols and the second set ofOFDM symbols comprising a useful portion and a cyclic prefix, wherein,to generate said each OFDM symbol, the processor is further configuredto: convert a block of frequency domain data to time-domain samplesusing an inverse fast Fourier transform having a transform size to formthe useful portion; and form the cyclic prefix by prepending to saideach OFDM symbol a plurality of time-domain samples from an end of theuseful portion, wherein the processor is further configured to form thefirst set of OFDM symbols using a first transform size and a firstcyclic prefix size, and to form the second set of OFDM symbols using asecond transform size different than the first transform size and asecond cyclic prefix size, and wherein the data frame further comprisesa plurality of parameters separately indicating the first cyclic prefixsize, the second cyclic prefix size, the first transform size, and thesecond transform size.
 12. The apparatus of claim 11, wherein the firstcyclic prefix size is different than the second cyclic prefix size. 13.The apparatus of claim 11, wherein the first transform size and thesecond transform size are each selected from a group consisting of:8192, 16384, and 32768 samples.
 14. The apparatus of claim 11, whereinthe first cyclic prefix size and the second cyclic prefix size are eachselected from a group consisting of: 192, 384, 512, 768, 1024, 1536,2048, 3072, and 4096 samples.
 15. The apparatus of claim 11, wherein thefrequency domain data comprises a set of useful subcarriers and a set ofnon-useful subcarriers.
 16. The apparatus of claim 15, wherein the dataframe further comprises a second plurality of parameters separatelyindicating a number of useful subcarriers in the first set of OFDMsymbols and a number of useful subcarriers in the second set of OFDMsymbols.
 17. A method, comprising: generating a data frame; andwirelessly broadcasting the data frame, wherein generating the dataframe comprises: generating a first set of orthogonal frequency domainmultiplexing (OFDM) symbols; and generating a second set of OFDMsymbols, wherein each OFDM symbol of the first set of OFDM symbols andthe second set of OFDM symbols comprises a useful portion and a cyclicprefix, and wherein generating said each OFDM symbol comprises:converting a block of frequency domain data to time-domain samples usingan inverse fast Fourier transform having a transform size to form theuseful portion; and forming the cyclic prefix by prepending to said eachOFDM symbol a plurality of time-domain samples from an end of the usefulportion of the OFDM symbol, wherein generating the data frame furthercomprises: forming the first set of OFDM symbols using a first transformsize and a first cyclic prefix size; and forming the second set of OFDMsymbols using a second transform size and a second cyclic prefix size,wherein the data frame comprises a plurality of parameters separatelyindicating the first cyclic prefix size, the second cyclic prefix size,the first transform size, and the second transform size, and wherein thefirst cyclic prefix size is selected from a group consisting of: 16, 24,32, 48, 96, 192, 384, 768, 1536, 3072, and 6144 samples.
 18. The methodof claim 17, wherein the first cyclic prefix size is different than thesecond cyclic prefix size.
 19. The method of claim 17, wherein the firsttransform size is different than the second transform size.